1. Field of the Invention
This invention generally relates to an internal combustion engine having an auxiliary intake or exhaust valve (or valves) in addition to main intake and exhaust valves for each cylinder, more particularly to an apparatus for actuating the valves.
2. Description of the Prior Art
Recently, multi-intake valve or multi-exhaust valve systems have been adopted in internal combustion engines for the purpose of increasing the engine output and decreasing the fuel consumption. In these systems, one (or two) auxiliary intake or exhaust valve is provided in addition to a pair of main intake and exhaust valves for each cylinder. A known means for actuating those valves is a twin cam shaft drive, wherein an auxiliary cam shaft is provided for the auxiliary value in addition to a cam shaft for the conventional main intake and exhaust valves. The provision of a twin cam shaft drive, however, not only means an increased number of cam shafts but also a more complex large and expensive drive. This is particularly serious in the case of an engine having a wedge-type combustion chamber, since there is not enough room to arrange the second cam shaft (auxiliary cam shaft). An improved drive mechanism of the valves has therefore been needed.
Alternatively, it has been known to actuate the valves by a single cam shaft. Such a known single cam shaft drive, however, needs two rocker arm shafts. Therefore, it also has the drawbacks of complexity, large size, and expensiveness of the valve drive, similar to the twin-cam shaft drive system.